Optical device alignment methods

ABSTRACT

In one method, a display source aligned with an illumination prism assembly is displaced along a displacement axis to adjust the distance between the display source and a collimating prism assembly. The display source, the illumination prism assembly, and an illumination module are translationally moved in unison in a plane normal to the displacement axis. In another method, a component of an optical device is coupled to a mechanical assembly at a known orientation. The mechanical assembly has a test pattern at a known orientation. An image sensor is aligned with the test pattern, and the image sensor captures an image of the test pattern. The captured image is analyzed to determine an estimated orientation of the test pattern. An orientation parameter of the image sensor is adjusted based on a comparison between the known orientation of the test pattern and the estimated orientation of the test pattern.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional PatentApplication No. 62/593,945, filed Dec. 3, 2017, whose disclosure isincorporated by reference in its entirety herein.

TECHNICAL FIELD

The present invention relates to methods and devices for aligningoptical devices and systems.

BACKGROUND OF THE INVENTION

During manufacture and assembly of image projecting optical devices, andmore specifically, micro-display projectors, it is necessary to alignand focus optical components of, and relating to, the optical device toachieve best performance. An example of a micro-display projector isdisclosed in U.S. Pat. No. 7,643,214 to Lumus Ltd., wherein a displaysource and collimating optics are assembled into the micro-displayprojector. Light waves corresponding to the image to be projected arecoupled into a light-guide optical element (LOE) by the micro-displayprojector that can be placed at the edge of the LOE, and can beconfigured in eyeglasses, such as embedded in the temple of theeyeglasses, or attached to a head-mounted display apparatus. Thecoupled-in light waves are guided through the LOE, by total internalreflection, and are coupled-out of the LOE as image light waves by oneor more partially reflecting surfaces and into an eye (or eyes) of auser (i.e., viewer).

In conventional focusing and alignment methods, the various opticalcomponents of the micro-display projector are moved, relative to eachother, via displacement and translations. However, such displacement andtranslations often result in the display source falling out of alignmentwith other major components of the micro-display projector, resulting indegradation in illumination uniformity. In addition, conventionalfocusing and alignment procedures typically rely on an image sensor(i.e., camera) capturing an image corresponding to light waves projectedby the micro-display projector. Using the example of the LOE and themicro-display projector disclosed in U.S. Pat. No. 7,643,214, aconventional focusing and alignment procedure would requireindependently moving the display source of the micro-display projectorto focus and align the components of the micro-display projector,coupling light waves from the micro-display projector into the LOE, andcapturing the light waves coupled-out of the LOE as an image. However,misalignment of the image sensor and the micro-display projector canlead to misalignment of the components of the micro-display projector.Specifically, if the image sensor is rotated about a principle axis(e.g., optical axis), then the display source will ultimately beincorrectly aligned with other components of the micro-displayprojector. This is a particular problem when using two optical systems(i.e., two micro-display projectors and two LOEs) with one opticalsystem deployed for each eye of a user, for example, as used in a stereovision system. If the micro-display projector of each optical system isnot properly aligned, each display source will provide an image at adifferent rotation angle, resulting in an incorrect stereo image.

SUMMARY OF THE INVENTION

The present invention is directed to methods for performing alignment ofoptical devices and systems.

According to the teachings of an embodiment of the present invention,there is provided a method for aligning and focusing components of anoptical device. The method comprises: displacing a display source alonga displacement axis to adjust a distance between the display source anda collimating prism assembly, the display source and an illuminationmodule being aligned with an illumination prism assembly such that lightwaves emitted by the illumination module arrive at the display sourcevia the illumination prism assembly; and translationally moving, inunison, the display source, the illumination prism assembly, and theillumination module in a plane normal to the displacement axis.

Optionally, the translationally moving includes moving the displaysource, the illumination prism assembly, and the illumination moduletogether as a single unit.

Optionally, the displacing includes moving the display source, theillumination prism assembly, and the illumination module together as asingle unit so as to adjust the size of a gap between the illuminationprism assembly and the collimating prism assembly.

Optionally, the display source and the illumination prism assembly arealigned so as to produce a gap between the display source and theillumination prism assembly.

Optionally, the displacing includes moving the display source so as toadjust the size of the gap between the display source and theillumination prism assembly.

Optionally, the method further comprises: mechanically coupling thedisplay source to the illumination prism assembly.

Optionally, the method further comprises: mechanically coupling theillumination module to the illumination prism assembly.

Optionally, the method further comprises: mechanically coupling thedisplay source to the illumination prism assembly.

Optionally, the method further comprises: mechanically coupling thecollimating prism assembly to the illumination prism assembly.

Optionally, the display source and the illumination module are alignedwith the illumination prism assembly such that the display source ispositioned along a first component of an optical axis of theillumination prism assembly, and the illumination module is positionedalong a second component of the optical axis of the illumination prismassembly that is orthogonal to the first axis.

Optionally, the display source and the illumination module aremechanically coupled to orthogonal surfaces of the illumination prismassembly.

Optionally, the collimating prism assembly and the illumination moduleare mechanically coupled to orthogonal surfaces of the illuminationprism assembly.

Optionally, the method further comprises: mechanically coupling at leastone of the display source, the illumination module and the collimatingprism assembly to the illumination prism assembly.

Optionally, the mechanically coupling includes cementing one or moreslabs of glass between the collimating prism assembly and theillumination prism assembly.

Optionally, the components of the optical device include the electronicdisplay source, the illumination module, the illumination prismassembly, and the collimating prism assembly, and the mechanicallycoupling including deploying a gel between at least two of thecomponents of the optical device.

Optionally, the method further comprises: mechanically coupling theillumination prism assembly and the illumination module to a mechanicalassembly at a known orientation, the mechanical assembly including atest pattern at a known orientation; capturing an image of the testpattern when the image sensor is positioned at a first location in whichthe image sensor is aligned with the test pattern; analyzing thecaptured image to determine an estimated orientation of the testpattern; adjusting an orientation parameter of the image sensor based ona comparison between the known orientation of the test pattern and theestimated orientation of the test pattern; and capturing an imageprojected by the optical device when the image sensor is positioned at asecond location in which the image sensor is aligned with the opticaldevice.

There is also provided according to an embodiment of the teachings ofthe present invention a method for aligning components of an opticaldevice. The method comprises: displacing a display source, anillumination module, and an illumination assembly, along a displacementaxis so as to adjust the size of a gap between the illumination prismassembly and a collimating prism assembly, the display source and theillumination module being aligned with the illumination prism assemblysuch that light waves emitted by the illumination module arrive at thedisplay source via the illumination prism assembly; and translationallymoving, in unison, the display source, the illumination prism assembly,and the illumination module in a plane normal to the displacement axis.

There is also provided according to an embodiment of the teachings ofthe present invention a method for aligning an image sensor with anoptical device. The method comprises: mechanically coupling at least onecomponent of the optical device to a mechanical assembly at a knownorientation, the mechanical assembly having a test pattern at a knownorientation; capturing an image of the test pattern when the imagesensor is positioned at a first location in which the image sensor isaligned with the test pattern; analyzing the captured image to determinean estimated orientation of the test pattern; and adjusting anorientation parameter of the image sensor based on a comparison betweenthe known orientation of the test pattern and the estimated orientationof the test pattern.

Optionally, the method further comprises: capturing an image projectedby the optical device when the image sensor is positioned at a secondlocation in which the image sensor is aligned with the optical device.

Optionally, the optical device includes an image projecting device and alight waves-transmitting substrate, the method further comprising:coupling light waves, corresponding to an image projected by the imageprojecting device, into the light waves-transmitting substrate; couplingthe coupled-in light waves out of the substrate as image light waves;and capturing the image light waves with the image sensor when the imagesensor is positioned at a second location in which the image sensor isaligned with the light waves-transmitting substrate.

Optionally, the orientation parameter of the image sensor includes anangle of rotation about a principle axis of the image sensor.

Optionally, the test pattern is vertically oriented relative to areference axis.

Optionally, the test pattern is horizontally oriented relative to areference axis.

-   -   Optionally, the test pattern is oriented at an oblique angle        relative to a reference axis.    -   Optionally, the orientation of the test pattern is defined by at        least one orientation parameter, and the at least one        orientation parameter of the test pattern includes an angular        position of the test pattern relative to a reference axis.

Optionally, the test pattern is formed as an aperture in the mechanicalassembly.

Optionally, the method further comprises: illuminating the test pattern.

Optionally, the method further comprises: moving the image sensor to thefirst location prior to capturing the image of the test pattern; andmoving the image sensor to the second location after capturing the imageof the test pattern.

Optionally, the optical device includes at least a display source, anillumination module, an illumination prism assembly, and a collimatingprism assembly.

Optionally, the method further comprises: aligning the illuminationmodule and the display source with the illumination prism assembly suchthat light waves emitted by the illumination module arrive at thedisplay source via the illumination prism assembly; displacing thedisplay source along a displacement axis to adjust a distance betweenthe display source and the collimating prism assembly; andtranslationally moving, in unison, the display source, the illuminationprism assembly, and the illumination module in a plane normal to thedisplacement axis.

Unless otherwise defined herein, all technical and/or scientific termsused herein have the same meaning as commonly understood by one ofordinary skill in the art to which the invention pertains. Althoughmethods and materials similar or equivalent to those described hereinmay be used in the practice or testing of embodiments of the invention,exemplary methods and/or materials are described below. In case ofconflict, the patent specification, including definitions, will control.In addition, the materials, methods, and examples are illustrative onlyand are not intended to be necessarily limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments of the present invention are herein described, by wayof example only, with reference to the accompanying drawings. Withspecific reference to the drawings in detail, it is stressed that theparticulars shown are by way of example and for purposes of illustrativediscussion of embodiments of the invention. In this regard, thedescription taken with the drawings makes apparent to those skilled inthe art how embodiments of the invention may be practiced.

Attention is now directed to the drawings, where like reference numeralsor characters indicate corresponding or like components. In thedrawings:

FIG. 1 is a top view illustrating a schematic representation of at leastan image projecting optical device, an LOE, an alignment module, animage sensor, and a mechanical assembly, deployed in an exampleenvironment in which embodiments of the present disclosure may beperformed;

FIG. 2 is a sectional view illustrating a schematic representation ofcomponents of an image projecting optical device having an electronicdisplay source, an illumination module, an illumination prism assembly,and a collimating prism assembly, that can be deployed in the exampleenvironment of FIG. 1 ;

FIG. 3A is a sectional view similar to FIG. 2 , showing the illuminationprism assembly and the collimating prism assembly deployed in spacedrelation, according to an embodiment of the present disclosure;

FIG. 3B is a sectional view similar to FIG. 3A, showing the electronicdisplay source, illumination module, and illumination prism assemblydisplaced relative to the collimating prism assembly, according to anembodiment of the present disclosure;

FIG. 3C is a sectional view similar to FIG. 3B, showing the electronicdisplay source, illumination module, and illumination prism assemblytranslated relative to the collimating prism assembly, according to anembodiment of the present disclosure;

FIG. 4A is a sectional view similar to FIG. 3A, showing the electronicdisplay source, the illumination prism assembly, and the collimatingprism assembly deployed in spaced relation, according to an embodimentof the present disclosure;

FIG. 4B is a sectional view similar to FIG. 4A, showing the electronicdisplay source displaced relative to the illumination prism assembly,according to an embodiment of the present disclosure;

FIG. 5 is a flow diagram illustrating a process for performing focusingand alignment of the components of the image projecting optical device,according to embodiments of the present disclosure;

FIG. 6 is a sectional view illustrating a schematic representation of analignment module used to perform orientation alignment of an imagesensor, according to an embodiment of the present disclosure;

FIGS. 7A and 7B are top views similar to FIG. 1 , showing the imagesensor deployed to align with the alignment module and the LOE,respectively, according to an embodiment of the present disclosure;

FIG. 8 is a schematic representation of a slit of the alignment module,deployed at an angle relative to the axis of motion of the image sensor,according to an embodiment of the present disclosure;

FIG. 9 is a schematic representation of an image of the slit captured bythe image sensor and sample points at respective edges of the image,according to an embodiment of the present disclosure;

FIG. 10 is a schematic representation of fit lines at respective edgesof the image of FIG. 9 , according to an embodiment of the presentdisclosure;

FIG. 11 is a flow diagram illustrating a process for performingorientation alignment of the image sensor, according to embodiments ofthe present disclosure;

FIG. 12 is a block diagram of an example architecture of an exemplaryprocessing system linked to the image sensor and a display monitor, forperforming one or more steps of the processes illustrated in FIGS. 5 and11 , according to an embodiment of the present disclosure;

FIG. 13 is an isometric view illustrating a schematic representation ofa mechanical assembly that can be used to perform embodiments of thepresent disclosure;

FIG. 14 is an isometric view of a sub-assembly of the mechanicalassembly, attached to components of the image projecting optical device,according to an embodiment of the present disclosure;

FIG. 15 is a block diagram of an example architecture of an exemplarycontrol system linked to the processing system, for performing one ormore steps of the processes illustrated in FIGS. 5 and 11 , according toan embodiment of the present disclosure; and

FIG. 16 is a sectional view illustrating a schematic representation ofan implementation of an LOE, according to an embodiment of the presentdisclosure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is directed to methods for performing alignment ofoptical devices and systems.

The principles and operation of the methods according to presentinvention may be better understood with reference to the drawingsaccompanying the description.

Before explaining at least one embodiment of the invention in detail, itis to be understood that the invention is not necessarily limited in itsapplication to the details of construction and the arrangement of thecomponents and/or methods set forth in the following description and/orillustrated in the drawings and/or the examples. The invention iscapable of other embodiments or of being practiced or carried out invarious ways. Initially, throughout this document, references are madeto directions such as, for example, upper and lower, top and bottom,left and right, and the like. These directional references are exemplaryonly to illustrate the invention and embodiments thereof.

Overview

Referring now to the drawings, FIG. 1 illustrates a schematicrepresentation of a top view of an image projecting optical device 10,an LOE 70, an alignment module 80, an image sensor and a display monitor100, deployed in an example environment 1 in which embodiments of thepresent disclosure may be performed. The environment 1 may be, forexample, an optical laboratory test bench with various types of optical,mechanical, and electronic testing equipment.

The environment 1 includes a mechanical assembly 60, to which the imageprojecting optical device 10 is mechanically attached together with theLOE 70. The mechanical assembly includes one or more attachmentmechanisms which hold the LOE 70 at a fixed and known orientation. TheLOE 70 is deployed at the fixed and known orientation using calibratedoptical test equipment, to ensure proper deployment of the LOE 70. Thealignment module 80 is also attached to the mechanical assembly 60 in afixed and known orientation. A sliding arrangement 66 attaches the imagesensor (i.e., camera) 90 to the mechanical assembly 60. The slidingarrangement 66 enables the image sensor 90 to slide between thealignment module 80 and the LOE 70. A first portion (i.e., base portion)of the sliding arrangement 66 slides along a railing deployed on a mainportion of the mechanical assembly 60. The image sensor 90 ismechanically attached to the sliding arrangement 66 at a second portion(i.e., distal portion from the base portion) via a mechanicalsub-assembly. The mechanical sub-assembly may be implemented as, forexample, a platform having one or more joints allowing for rotationalthree degrees of freedom.

The display monitor 100, implemented, for example, as a liquid crystaldisplay (LCD) or the like, is connected to the image sensor 90 via aninterface connection 102. The interface connection 102 can beimplemented, for example, as a cable connected to respectiveinput/output ports of the image sensor 90 and the display monitor 100.The display monitor 100 is operative to display images captured by theimage sensor 90 for viewing by a user or operator of the environment 1.The display monitor 100 may function as a viewfinder for the imagesensor 90, allowing the user or operator to see changes in imagescaptured by the image sensor 90 in response to user initiated mechanicaladjustments made to various components of the mechanical assembly 60.

The mechanical assembly 60 may include one or more sub-assemblies, eachconfigured for holding different optical and/or mechanical components.In certain embodiments, the mechanical assembly 60 includes at leastthree major sub-assemblies, namely a first sub-assembly 61, a secondsub-assembly 63, and a third sub-assembly 65. The first sub-assembly 61holds components of the image projecting optical device 10 and attachesthe components of the image projecting optical device 10 to themechanical assembly 60. The second sub-assembly 63 holds the LOE 70 andattaches the LOE 70 to the mechanical assembly 60. The sub-assemblies61, 63 are arranged to allow cooperative positioning of the imageprojecting optical device 10 and the LOE 70, such that the light wavesproduced by the image projecting optical device 10 are coupled in to theLOE 70. The third sub-assembly 65 holds the alignment module 80 andattaches the alignment module 80 to the mechanical assembly 60.

The sub-assemblies 61, 63, 65 may be implemented in various ways,including, but not limited to, bracket arrangements, grippingarrangements, and pin/screw arrangements. In certain embodiments, thefirst sub-assembly 61 can be arranged to hold the electronic displaysource 12, the illumination module 14, and the illumination prismassembly 16, while the second sub-assembly 63 may be arranged to holdthe LOE 70 and the collimating prism assembly 18. The mechanicalassembly 60, and the corresponding sub-assemblies 61, 63, 65, arearranged to maintain the alignment and orientation of the components ofthe image projecting optical device 10, the LOE 70, and alignment module80, respectively. It is noted that the sub-assemblies 61, 63, 65, inparticular the first sub-assembly 61, may include one or moresub-components to allow for controlled adjustment of the positioning ofthe components which are held by the sub-assembly. Such controlledadjustment will be described in detail in subsequent sections of thepresent disclosure.

Generally speaking, the embodiments of the present disclosure aredirected to a two-stage alignment (i.e., calibration) process. In one ofthe stages, referred to as a focusing and alignment stage, theindividual components of the image projecting optical device 10 arefocused and aligned such that the image projecting optical device 10produces a sharp and focused image at the LOE 70 output. The focusingand alignment is performed by moving sub-components of the imageprojecting optical device 10 while evaluating image quality metrics ofimages captured by the image sensor 90 at the LOE 70 output untilcertain performance criteria are met. Prior to performing the steps ofthe focusing and alignment stage, the image sensor 90 is focused toinfinity and positioned across from the LOE 70 (i.e., aligned with theLOE 70) at an eye relief distance from the LOE 70 (for example 18millimeters), and preferably within an eye motion box, to enablecapturing of the image light waves that are coupled out of the LOE 70.The eye motion box is a two-dimensional area in which the eye (or imagesensor 90) has a full field of view (FOV) of the image light rayscoupled out of the LOE 70, which correspond to the entire input image,generated by the image projecting optical device 10, that is coupledinto the LOE 70. In this way, the image sensor 90 acts as the human eye,and the images displayed on the display monitor 100 act as the imagesthat would be seen by the eye of the viewer when using the opticaldevice/system (i.e., the LOE 70 together with the image projectingoptical device 10), for example when the viewer wears eyeglasses intowhich the image projecting optical device 10 and the LOE 70 areembedded.

In the other stage, referred to as an orientation alignment stage, theorientation of the image sensor 90 is adjusted so as to align with theorientation of the alignment module 80, which is linked to the alignmentorientation of the LOE 70. The alignment of the image sensor 90 with thealignment module 80 allows for proper execution of the focusing andalignment stage, in which the components of the image projecting opticaldevice 10 are aligned and focused.

With continued reference to FIG. 1 , refer now to FIG. 2 , a sectionalview illustrating a schematic representation of components of anon-limiting example of the image projecting optical device 10 for whichthe focusing and alignment methods according to embodiments of thepresent disclosure are to be performed. Generally speaking, the imageprojecting optical device 10 includes an electronic display source 12,an illumination module 14, an illumination prism assembly 16, and acollimating prism assembly 18. In a non-limiting implementation, theelectronic display source 12 is implemented as a liquid crystal onsilicon (LCoS) micro-display.

The illumination module 14 includes a light source and is configured totransmit light in order to illuminate the image area of the electronicdisplay source 12. The illumination module 14 may be implemented invarious ways, and may be a polarized or unpolarized light source.Examples of non-limiting implementations of the light source of theillumination module 14 include, but are not limited to, a light emittingdiode (LED), a light pipe with red-green-blue (RGB) LEDs for colormixing, multiple LEDs that each emit a different color in combinationwith dichroic mirrors for color mixing, a diode laser, and multiplediode lasers that each emit a different color in combination withdichroic mirrors for color mixing.

According to certain non-limiting implementations, such as theimplementation illustrated in FIG. 2 , the light source of theillumination module 14 is a polarized light source, and morespecifically is a source that produces s-polarized light waves. Theillumination prism assembly 16 receives the s-polarized light waves fromthe illumination module 14 through a light-transmissive surface 32 of afirst prism 20 of the illumination prism assembly 16. The receiveds-polarized light waves are reflected off of a p-polarizationtransmissive polarizing beamsplitter 24 (which transmits p-polarizedlight and reflects s-polarized light) and coupled out of theillumination prism assembly 16 toward the electronic display source 12through a light-transmissive surface 34 of the first prism 20. Thepolarizing beamsplitter 24 is positioned between a slant edge of thefirst prism 20 and a slant edge of a second prism 22 of the illuminationprism assembly 16. In response to the received illumination of thes-polarized light waves at the image area of the electronic displaysource 12, the electronic display source 12 is stimulated (i.e.,activated) to generate corresponding pixel output in the form ofp-polarized light waves emanating from the active pixels of theelectronic display source 12. The p-polarized light waves from theelectronic display source 12 are coupled into the illumination prismassembly 16 through the light-transmissive surface 34 and pass throughthe polarizing beamsplitter 24. The p-polarized light waves are thencoupled out of the illumination prism assembly 16 through alight-transmissive surface 36 of the second prism 22 and toward thecollimating prism assembly 18.

Prior to being coupled into the collimating prism assembly 18 the lightwaves may pass through a half-wavelength retardation plate (not shown)to convert the p-polarized light waves to s-polarized light waves.

According to certain non-limiting implementations, such as theimplementation illustrated in FIG. 2 , the s-polarized light waves arecoupled into the collimating prism assembly 18 through alight-transmissive surface 38 of a first prism 26 of the collimatingprism assembly 18. The coupled-in s-polarized light waves reflect off ofa p-polarization transmissive polarizing beamsplitter 30 (whichtransmits p-polarized light and reflects s-polarized light) that ispositioned between a slant edge of the first prism 26 and a slant edgeof a second prism 28 of the collimating prism assembly 18. Although notshown in the drawings, collimating lenses, together withquarter-wavelength retardation plates, may be positioned at opposinglight-transmissive surfaces 40, 42 of the prisms 26, 28 so as to act tocollimate the light waves that ultimately exit the collimating prismassembly 18. Accordingly, the s-polarized light waves reflect off of thepolarizing beamsplitter 30, are coupled out of the collimating prismassembly 18 through the light-transmissive surface 40, pass through aquarter-wavelength retardation plate, are reflected by a collimatinglens, return to pass again through the quarter-wavelength retardationplate (thereby converting the light waves to p-polarized light waves),and re-enter the collimating prism assembly 18 through thelight-transmissive surface 40. The p-polarized light waves then passthrough the polarizing beamsplitter 30, are coupled out of thecollimating prism assembly 18 through the light-transmissive surface 42,pass through a quarter-wavelength retardation plate, are reflected by acollimating lens, return to pass again through the quarter-wavelengthretardation plate (thereby converting the light waves to s-polarizedlight waves), and re-enter the collimating prism assembly 18 through thelight-transmissive surface 42. The now s-polarized light waves arereflected off of the polarizing beamsplitter 30 and are coupled out ofthe collimating prims assembly 18 through a light-transmissive surface44 of the second prism 28, where they may be coupled into alight-transmissive substrate (e.g., LOE) and ultimately coupled out ofthe substrate into the eye of a viewer. The coupling-in of light wavesmay be accomplished via an in-coupling optical surface (e.g., awedge-shaped prism or an angled reflecting surface) that interfaces thecollimating prism assembly 18 and the LOE input.

Note that for each instance where a particular polarized wave path hasbeen followed in the examples described above, the polarizations areinterchangeable. In other words, on altering the orientation of thepolarizing beamsplitters, each mention of p-polarized light could bereplaced by s-polarized light, and vice versa. As such, the specific useof the particular beamsplitters in the illumination prism assembly 16and the collimating prism assembly 18 in the examples described aboveare not intended to be limiting, are provided for illustrative purposesin order to better describe the operation of the image projectingoptical device 10.

Also note that the light-transmissive surfaces of the prisms of theillumination prism assembly 16 and the collimating prism assembly 18described above are generally planar surfaces. As should be apparent,the light-transmissive surfaces 34, 36, 38, 44 are parallel to eachother (i.e., are in parallel planes), and are orthogonal to thelight-transmissive surface 32.

Although it should be noted that the components of the image projectingoptical device are not necessarily drawn to scale in FIG. 2 , it shouldbe clear from FIG. 2 that the electronic display source 12, theillumination module 14, the illumination prism assembly 16, and thecollimating prism assembly 18 are out of alignment, causingnon-uniformity of the illumination of the electronic display source 12,and ultimately resulting in a non-uniform and defocused image.Accordingly, focusing and alignment of the major components of the imageprojecting optical device 10 should be performed to ensure uniformity ofthe illumination of the electronic display source 12. The followingparagraphs describe the focusing and alignment stage in detail.

Focusing and Alignment Stage

Referring now to FIGS. 3A-3C, focusing and alignment of the componentsof the image projecting optical device 10 according to an embodiment ofthe present disclosure. In FIG. 3A, the illumination prism assembly 16is deployed in spaced relation relative to the collimating prismassembly 18 so as to produce and provide a gap 46 between theillumination prism assembly 16 and the collimating prism assembly 18.The size of the gap 46 is measured as the shortest distance between thelight transmissive surfaces 36, 38 (i.e., the distance along the linethat is normal to, and bounded by, the light transmissive surfaces 36,38). In certain embodiments, the gap 46 is a spatial gap implemented asan air gap, while in other embodiments the gap 46 is implemented as alight-transmissive gel deployed between the light-transmissive surfaces36, 38. In yet other embodiments, the gap 46 is implemented as acombination of an air gap and an optical component, for example, a lensthat is optically attached to the light-transmissive surface 38 of thecollimating prism assembly 18.

The initial size of the gap 46 may vary depending on how the componentsof the image projecting optical device 10 are initially assembled. Intypical configurations, the size of the gap 46 is less than 1millimeter, and in common implementations is approximately 0.5millimeters. The initial gap size (i.e., width) is denoted as W G inFIG. 3A. The illumination module 14 is mechanically attached to theillumination prism 16 at the light-transmissive surface 32. Themechanical attachment is made via an alignment mechanism that in certainembodiments is a sub-component of the first sub-assembly 61 of themechanical assembly 60. The alignment mechanism also aligns theillumination module 14 with the nominal optical axis of the imageprojecting optical device 10.

In general terms, the optical axis of the image projecting opticaldevice 10 is defined in part by the illumination prism assembly 16, andfurther in part by the collimating prism assembly 18. The optical axisof the image projecting optical device 10 includes multiple components,which as illustrated in FIG. 3A includes a first component 48 a of theoptical axis and a second component 48 b of the optical axis that isorthogonal to the first component 48 a. The first component 48 a isnormal to the plane in which the light-transmissive surface 32 lies, andthe second component 48 b is normal to the plane in which thelight-transmissive surface 34 lies.

As such, the aforementioned alignment mechanism aligns the illuminationmodule 14 with the first component 48 a of the optical axis. Theelectronic display source 12 is aligned, via an alignment mechanism, tothe second component 48 b. The same alignment mechanism may be used toalign the electronic display source 12 and the illumination module 14.Alternatively, the alignment mechanism that aligns the electronicdisplay source 12 may be a sub-component of the first sub-assembly 61that is a different sub-component from the alignment mechanism thataligns the illumination module 14.

The electronic display source 12 and the illumination module 14 arealigned with the illumination prism assembly 16 such that the lightwaves emitted by the illumination module 14 reflect off of thepolarizing beamsplitter 24 and arrive at the image area of theelectronic display source 12 so as to uniformly illuminate theelectronic display source 12. The image area of the electronic displaysource 12 is generally located at a central region of the front portionof the electronic display source 12 (i.e., the center of the LCoS). Thealignment of the electronic display source 12 may include moderatelytilting or rotating the electronic display source 12 about the X-axis,and/or Y-axis, and/or the Z-axis.

The electronic display source 12 may be attached (for example viaoptical cement) to the light-transmissive surface 34 of the first prism20. Alternatively, the electronic display source 12 may be heldmechanically in place next to the light-transmissive surface 34 of thefirst prism 20 with or without an air gap provided between theelectronic display source 12 and the light-transmissive surface 34 ofthe first prism 20. The electronic display source 12 may be helpmechanically by a sub-component of the first sub-assembly 61.

The electronic display source 12, the illumination module 14, and theillumination prism assembly 16 are displaced (i.e., shifted), in unisonas a single unit 50 (i.e., single mechanical unit of the firstsub-assembly 61, demarcated by dashed lines), along a displacement axisthat is colinear with the second component 48 b, which in FIGS. 3A-3C isthe Z-axis. By equivalence, the displacement occurs along a line that isnormal to the light-transmissive surface 34 of the first prism 20. Thedisplacing action effectively moves the electronic display source 12closer to, or further away from, the collimating prism assembly 18,thereby adjusting the shortest linear distance between the electronicdisplay source 12 and the collimating prism assembly 18. The lineardistance, denoted as D in FIG. 3A, is a direct function of the size ofthe gap 46 introduced by the deployment of the illumination prism 16.Specifically, the linear distance D is approximately equal to the sum ofthe gap width W_(G), the width of the illumination prism assembly 16(i.e., the shortest distance between the transmissive surfaces 34 and36), and the distance between the front panel of the electronic displaysource and the illumination prism assembly 16. In embodiments in whichthe electronic display source 12 is cemented to the light-transmissivesurface 34 of the first prism 20, the distance between the front panelof the electronic display source 12 and the illumination prism assembly16 is approximately equal to the layer thickness of the optical cementused to attach the electronic display source 12 to thelight-transmissive surface 34.

As the linear distance changes, the size of the gap 46 also changes, asdoes the position of the focal plane of the image projecting opticaldevice 10. As the position of the focal plane changes, the focus of theimage, projected by the image projecting optical device 10, and capturedby the image sensor 90 at the output of the LOE 70, also changes. Thedisplacing action is performed while evaluating an image quality metric,more specifically focus quality, of the captured image, and is performeduntil a best focus of the captured image is achieved. The image qualitymetric (i.e., focus quality) of the image may be evaluated, for example,via image processing techniques and methods (performed by a computerizedprocessor, e.g., an image processor), to provide an indication of thedistance adjustment (i.e., between the electronic display source 12 andthe collimating prism assembly 18) required in order to achieve bestfocus. The image processing techniques may include, for example,evaluating the modulation transfer function (MTF) at the detector of theimage sensor 90. Alternatively, or in combination with image processingtechniques, the focus quality may be visually evaluated by the operatorof the environment 1 by viewing the images, from the image sensor 90,displayed on the display monitor 100. Accordingly, as the operatordisplaces the electronic display source 12 so as to adjust the positionof the focal plane, the MTF and/or the focus of the image displayed onthe display monitor 100 changes. The displacement of the electronicdisplay source 12 is continued until the focal plane is at a position inwhich the MTF indicates that the image is in focus and/or the operatorviews a focused image on the display monitor 100.

FIG. 3B shows the electronic display source 12, the illumination module14, and the illumination prism 16 subsequent to the linear displacementto achieve best focus, in which the size of the gap 46 is reduced to avalue of less than W G as a result of movement of the single unit closerto the collimating prism assembly 18. The size of the gap 46, afterachieving best focus, is denoted as W_(F) in FIG. 3B.

Once the distance between the electronic display source 12 and thecollimating prism assembly 18 is properly adjusted to ensure best focus,the unit 50 is translationally moved. The unit 50 is translationallymoved relative to the light-transmissive surface 38 of the collimatingprism assembly 18, and in the plane normal to the displacement axis,which in FIGS. 3A-3C is the XY-plane. In other words, the unit 50 istranslated in a plane parallel to the plane of the light-transmissivesurfaces 34, 36, 38. The translational movement of the single unit 50 inthe XY-plane is performed without rotation (i.e., without rotation aboutthe displacement axis (i.e., the Z-axis) or the X-axis or the Y-axis).The translation is performed so as to maintain the alignment of theelectronic display source 12 and the illumination module 14 with theillumination prism assembly 16, and to maintain line of sight (LoS) ofthe optical system (i.e., between the image projecting optical device 10and the LOE 70). Within the context of this document, the term “LoS”generally refers to when there is a correspondence between theappropriate individual pixels of the LOE 70 output image and the activepixels of the image area of the electronic display source 12. When LoSis maintained, the image sensor 90, when positioned in the eye motionbox at the eye relief distance, captures the entire image (i.e., fullFOV) projected by the LOE 70. For example, LoS may not be achieved ifthe unit 50 is translationally offset from the collimating prismassembly 18 by more than an allowed amount. In such instances, some ofthe pixels of the source image (i.e., from the electronic display source12) may not reach the LOE 70 output even when the image sensor 90 iswithin the eye motion box, the results of which may be manifested in acutoff image when viewing the LOE 70 output image on the display monitor100 (or equivalently when the image light waves are coupled out of theLOE 70 and into the eye(s) of a viewer).

FIG. 3C shows the components of the image projecting optical device 10subsequent to translational movement in the XY-plane. The LoS may beevaluated via image processing techniques (performed by a computerizedprocessor, e.g., an image processor), or may be visually evaluated bythe user by viewing the output images from the LOE 70, captured by theimage sensor 90, displayed on the display monitor 100. For example,while the LOE 70 output image is viewed by the user on the displaymonitor 100, the unit 50 may be translated in the XY-plane untilappropriate pixel matching, corresponding to the desired LoS, isachieved. By translating the electronic display source 12, theillumination module 14, and the illumination prism assembly 16 togetheras a single unit, uniform illumination of the electronic display source12 by the illumination module 14 (via the illumination prism assembly16) is maintained. As such, the center of the electronic display source12 is illuminated throughout the duration of the translational movementin the XY-plane.

After the translational movement of the single unit 50 is complete, theillumination prism assembly 16 and the collimating prism assembly 18 maybe optically attached to each other at light-transmissive surfaces 36,38, for example via optical cement. As a result, the major components ofthe image projecting optical device 10 are connected to each other,either directly or indirectly.

Although embodiments of the disclosure described thus far have pertainedto displacing and translating the electronic display source 12 togetherwith the illumination module 14 and the illumination prism assembly 16as a single unit, other embodiments are possible in which the electronicdisplay source 12 is displaced independently from the illuminationmodule 14 and the illumination prism assembly 16.

Refer now to FIGS. 4A-4B, focusing and alignment of the components ofthe image projecting optical device 10 according to another embodimentof the present disclosure. In FIG. 4A, the electronic display source 12and the illumination prism assembly 16 are deployed in spaced relationrelative to the collimating prism assembly 18 so as to produce andprovide two gaps, namely a first gap 47 a and a second gap 47 b. Thefirst gap 47 a is provided between the illumination prism assembly 16and the collimating prism assembly 18, similar to the gap 46 describedin the embodiments with reference to FIGS. 3A-3C, and should beunderstood by analogy thereto. The second gap 47 b is provided betweenthe electronic display source 12 and the illumination prism 16. The sizeof the second gap 47 b is measured as the shortest distance between thefront panel of the electronic display source 12 and thelight-transmissive surface 34 (i.e., the distance along the line that isnormal to, and bounded by, front panel of the electronic display source12 and the light-transmissive surface 34). In certain embodiments, thesecond gap 47 b is a spatial gap implemented as an air gap.

The initial sizes of the gaps 47 a, 47 b may vary depending on how thecomponents of the image projecting optical device 10 are initiallyassembled. In FIG. 4A the initial size (i.e., width) of the first gap 47a is denoted as W_(G1) and the initial size of the second gap 47 b isdenoted as W_(G2).

The electronic display source 12 and the illumination module 14 arealigned with the illumination prism assembly 16 such that the lightwaves emitted by the illumination module 14 reflect off of thepolarizing beamsplitter 24 and arrive at the image area of theelectronic display source 12 so as to uniformly illuminate theelectronic display source 12. In addition to aligning the illuminationmodule 14 with the illumination prism assembly 16, the illuminationmodule 14 is mechanically attached to the illumination prism assembly 16at the light-transmissive surface 32 via a sub-component of the firstsub-assembly 61.

The electronic display source 12 is then displaced along thedisplacement axis (i.e., the axis colinear with the second component 48b, i.e., the axis that is orthogonal to the light-transmissive surface34) while the illumination module 14 and the illumination prism assembly16 are held in place (i.e., are static). The electronic display source12 is displaced to adjust the size of the second gap 47 b. Thedisplacing action effectively moves the electronic display source 12closer to, or further away from, the illumination prism assembly 16 andthe collimating prism assembly 18, thereby adjusting the shortest lineardistance between the electronic display source 12 and the collimatingprism assembly 18. The linear distance, denoted as D₁ in FIG. 4A, is adirect function of the size of the gaps 47 a, 47 b. Specifically, thelinear distance D₁ is approximately equal to the sum of the gap widthsW_(G1) and W_(G2), and the width of the illumination prism assembly 16(i.e., the shortest distance between the transmissive surfaces 34 and36.

Similar to as described above with reference to FIGS. 3A-3C, theelectronic display source 12 is displaced until best focus is achieved.FIG. 4B shows the electronic display source 12 subsequent to the lineardisplacement to achieve best focus, in which the size of the second gap47 b is reduced to a value of less than W_(G2) as a result of movementof the electronic display source 12 closer to the collimating prismassembly 18. As shown in FIG. 4B, the size of the first gap 47 a remainsunchanged. The size of the second gap 47 b, after achieving best focus,is denoted as W_(F2) in FIG. 4B.

Once best focus is achieved, the electronic display source 12 ismechanically attached to the illumination prism assembly 16 at thelight-transmissive surface 34. The mechanical attachment may beeffectuated by one or more sub-components of the first sub-assembly 61.The electronic display source 12, the illumination module 14, and theillumination prism assembly 16 are then translated, as a single unit(i.e., unit 50), in the XY-plane, so as to maintain the desired LoS, ina manner similar to as described with reference to FIG. 3C.

In certain embodiments, displacement along the displacement axis may beinitiated so as to adjust the size of both gaps 47 a and 47 b. In suchembodiments, the electronic display source 12 is displaced to adjust thesize of the second gap 47 b, while the illumination prism assembly 16 isdisplaced along the displacement axis (i.e., the Z-axis), together withthe illumination module 14, to adjust the size of the first gap 47 a.

The embodiments described with reference to FIGS. 3A-3C has certainadvantages over methods that rely on using gaps close to the electronicdisplay source 12, for example, in the embodiments described withreference to FIGS. 4A-4B. One such advantage is that the imageprojecting optical device 10 performs better optically when there is nogap between the electronic display source 12 and the illumination prismassembly 16 (i.e., the second gap 47 b). By not having a gap close tothe electronic display source 12, the area close to the focal plane ofthe image projecting optical device 10 remains clean and free fromcontaminants.

As discussed above, the major components of the image projecting opticaldevice 10 are connected to each other, either directly or indirectly.The connections are effectuated by mechanical attachment of the majorcomponents via one or more sub-components of the first sub-assembly 61.In certain embodiments, the mechanical attachment between theillumination prism assembly 16 and the collimating prism assembly 18 iseffectuated by one or more glass slabs that are cemented to thelight-transmissive surfaces 36, 38. In other embodiments, alight-transmissive gel is placed between adjacent components of theimage projecting optical device in order to fill unwanted gaps betweensuch components. For example, the gel may be deployed between theillumination module 14 and the illumination prism assembly 16.

Attention is now directed to FIG. 5 which shows a flow diagram detailinga process 500 in accordance with the disclosed subject matter. Theprocess 500 includes steps for focusing and aligning the components ofthe image projecting optical device 10. Some of the sub-processes of theprocess 500 may be performed manually by an operator of the environment1 or may be performed automatically by various mechanical andcomputerized components, such as processors and the like.

The process 500 begins at block 502, where the illumination prismassembly 16 is deployed relative to the collimating prism assembly 18 soas to produce a gap (i.e., the gap 46, or the first gap 47 b) betweenthe illumination prism assembly 16 and the collimating prism assembly18. The process 500 then moves to block 504, where the illuminationmodule 14 and the electronic display source 12 are aligned with theillumination prism assembly 16 such that the light waves emitted by theillumination module 14 arrive at the image area of the electronicdisplay source 12, via reflection off of the polarizing beamsplitter 24,so as to uniformly illuminate the electronic display source 12. Thealigning step includes positioning the electronic display source 12along the first component 48 a of the optical axis of the illuminationprism assembly 16 such that the first component 48 a passes through thecenter of the electronic display source 12, and positioning theillumination module 14 along the second component 48 b of the opticalaxis of the illumination prism assembly 16 such that the secondcomponent 48 b passes through the center of the illumination module 14.

In certain embodiments, the aligning performed in block 504 includesmechanically attaching the electronic display source 12 and theillumination module 14 to respective surfaces of the illumination prismassembly 16 (i.e., the orthogonal light-transmissive surfaces 32, 34).In other embodiments, the aligning performed in block 504 includesproducing a gap (i.e., the second gap 47 b) between the electronicdisplay source 12 and the illumination prism assembly 16.

The process 500 then moves to block 506, where the electronic displaysource 12 is displaced along the displacement axis (i.e., the Z-axis) toadjust the distance between the electronic display source 12 and thecollimating prism assembly 18 in order to achieve best focus. In otherwords, by displacing the electronic display source 12, the position ofthe focal plane of the image projecting optical device 10 is adjusted.The focal plane position is adjusted while image quality metrics areevaluated (e.g., MTF) in order to achieve best (i.e., optimal) ornear-best focus of the image projected by the image projecting opticaldevice 10. In certain embodiments, the electronic display source 12 isdisplaced together with the illumination module 14 and the illuminationprism assembly 16, such they are displaced in unison, together as asingle unit.

In other embodiments, the electronic display source 12 is displacedalone while the illumination module 14 and the illumination prismassembly 16 remain static. In such embodiments, the electronic displaysource 12 is mechanically attached to the illumination prism assembly 16subsequent to performing the displacing of block 506.

As discussed above, the best focus may be determined by evaluating thefocus quality of the image (captured by the image sensor 90 at the LOE70 output), via image processing techniques and methods, such as, forexample, determining the MTF.

The process 500 then moves to block 508, where the electronic displaysource 12, the illumination module 14, and the illumination prism 16 aretranslated in unison in the XY-plane in order to maintain the desiredLoS. The LoS may be evaluated via image processing techniques. Asdiscussed above, in certain embodiments the translational movement iseffectuated by moving the electronic display source 12, the illuminationmodule 14, and the illumination prism 16 together as a single unit.

As mentioned above, the embodiments directed to methods for performingfocusing and alignment of the components of the image projecting opticaldevice 10 constitutes one stage (referred to as the focusing andalignment stage) of a two-stage process. The other stage, referred to asthe orientation alignment stage, is performed in order to ensure thatthe image sensor 90 is properly aligned with the image projectingoptical device 10, so that the images captured by the image sensor 90during execution of the method steps of the focusing and alignment stageenable proper alignment of the electronic display source 12 with theremaining components of the image projecting optical device 10. Thefollowing paragraphs describe the orientation alignment stage in detail.

Orientation Alignment Stage

Referring again to FIG. 1 , the alignment module 80 is attached to themechanical assembly 60 at a first portion 62 a thereof via the thirdsub-assembly 65. The image projecting optical device 10 and the LOE 70are mechanically attached to the mechanical assembly 60 at a secondportion 62 b thereof via the first sub-assembly 61 and the secondsub-assembly 63, respectively. The image projecting optical device 10,the LOE 70, and the alignment module 80 are held in known fixedorientations by the respective sub-assemblies 61, 63, 65.

In certain embodiments, the mechanical assembly 60 includes a centralportion 64 that provides physical separation between the two portions 62a, 62 b. The two portions 62 a, 62 b may be located at opposite ends ofthe mechanical assembly 60, separated by the central portion 64.

The image sensor 90 is attached to the mechanical assembly 60 via thesliding arrangement 66. The sliding arrangement 66 is operative to slidehorizontally between two positions so as to alternately align the imagesensor 90 with the LOE 70 and the alignment module 80.

With continued reference to FIG. 1 , refer now to FIG. 6 a sectionalview illustrating a schematic representation of the alignment module 80according to an embodiment of the present disclosure. The alignmentmodule 80 includes a test pattern 86. In a preferred but non-limitingimplementation, the test pattern 86 is implemented as a generallyrectangular slit (i.e., an elongated aperture) formed in a base surfaceof the alignment module 80. In other embodiments, the test pattern 86can be a printed pattern, for example, an elongated rectangular pattern,printed on a base surface of the alignment module 80. In certainembodiments, the alignment module 80 is a component of the mechanicalassembly 60, and therefore the test pattern 86 may be considered as aportion of the mechanical assembly 60, formed as an aperture or anopening in the mechanical assembly 60.

The test pattern 86 is positioned at a fixed and known orientation withrespect to the mechanical assembly 60. The orientation of the testpattern 86 is defined by one or more orientation parameters. Accordingto embodiments of the present disclosure, the angle of the central axisof the test pattern 86 relative to a reference axis defines the mainorientation parameter. In implementations in which the test pattern isimplemented as a rectangular slit, the central axis is the long line ofreflectional symmetry of the rectangle. The reference axis may be, forexample, the axis of horizontal movement of the image sensor 90, whichis the plane of the paper in FIG. 6 , or may be the vertical axis thatis normal to the axis of horizontal movement of the image sensor 90. Aswill described in greater detail below, the image sensor 90 is operativeto capture one or more images of the test pattern 86 when the imagesensor 90 is aligned with the alignment module 80 in order to allowestimation of the orientation parameter (i.e., angle) of the testpattern 86 via image processing algorithms.

In certain embodiments, such as the non-limiting embodiment illustratedin FIG. 6 , the test pattern 86 is illuminated from the back in order toproduce a clearer and sharper image of the test pattern 86. In suchembodiments, a diffuser 84 is deployed between the test pattern 86 and alight source 82, implemented, for example, as one or more light emittingdiodes (LEDs). Light waves (represented schematically as light rays 83)emanating from the light source 82 are scattered by the diffuser 84. Thescattered light waves (represented schematically as light rays from thediffuser 84 illuminate the back of the test pattern 86.

Refer now to FIG. 7A, the sliding arrangement 66 in a first position soas to position the image sensor 90 in a first location. When the imagesensor 90 is in the first location, the lens 92 (which may includemultiple lenses) of the image sensor 90 is aligned with the alignmentmodule such that the test pattern 86 is positioned within the field ofview of the lens 92.

FIG. 8 shows a front view of the test pattern 86, when implemented as aslit, taken from the perspective of the image sensor 90 when the imagesensor 90 is aligned with the alignment module 80 (FIG. 7A). The testpattern 86 may generally be deployed at any known and fixed orientation,including vertically, horizontally, or any angle therebetween. However,orienting the test pattern 86 at an angle of approximately 30°, asillustrated in FIG. 8 , is advantageous when utilizing certain imageprocessing algorithms (e.g., edge detection algorithms), as such anorientation provides the algorithm with more clearly defined edgeregions, thereby more easily accommodating estimation of the orientationof the test pattern 86. As discussed above, the angle is measured fromthe central axis 87 of the test pattern 86 to the reference axis, whichin FIG. 8 is the axis of horizontal movement of the image sensor 90.

With continued reference to FIG. 7A, the image sensor 90 captures one ormore images of the test pattern 90 when image sensor 90 is in the firstlocation. When in the first location, the lens 92 of the image sensor 90is spaced apart from the test pattern 86 by approximately 10-15centimeters. As mentioned above when discussing the focus and alignmentstage, the image sensor 90 is focused to infinity when capturing theimage light waves that are coupled out of the LOE 70. Since it ispreferable to keep the image sensor 90 at a fixed focus (i.e.,permanently focused to infinity), images of the test pattern 86 arepreferably captured with the aperture of the image sensor 90 in adecreased aperture state, in order to ensure a sharp image in which theedges of the test pattern 86 are distinct and can be more easilyidentified by image processing algorithms.

The images captured by the image sensor 90, when the image sensor 90 isin the first location, are analyzed by a computerized processor (e.g.,an image processor) linked to the image sensor 90 in order to estimatethe orientation (i.e., angle) of the test pattern 86. The processorcompares the estimated orientation of the test pattern 86 to the knowntrue orientation of the test pattern 86. In certain embodiments, thecomparison forms a comparison measure, which may be, for example, formedby taking the absolute value of the difference between the estimatedorientation and the known orientation. In such embodiments, adetermination is made, by the computerized processor, as to whether theestimated orientation is within an allowed tolerance (e.g., +/−τ°). Ifthe estimated orientation is within the allowed tolerance, the imagesensor 90 is deemed as being properly aligned. If, however, theestimated orientation is not within the allowed tolerance, theorientation parameter of the image sensor 90 is adjusted. In certainembodiments, the adjustment of the orientation parameter of the imagesensor 90 is performed via rotation of the image sensor (via thesub-assembly that attaches the image sensor 90 to the slidingarrangement 66) about a principle axis of the image sensor 90, which maybe the optical axis of the lens 92. Subsequent to the orientationparameter adjustment, another image is captured by the image sensor 90,and the analysis and comparison steps, outlined above, are repeated,until the estimated orientation is within the allowed tolerance. Theindication of whether the estimated orientation is within the allowedtolerance may be provided in real-time, so as to allow an operator ofthe environment 1 to continuously adjust the orientation parameter ofthe image sensor 90 until a stopping condition is met (i.e., until theestimated orientation of the test pattern 86 is within the allowedtolerance). In this way, the orientation parameter (i.e., angle) of theimage sensor 90 is adjusted, by the operator, so as to converge towithin the allowed tolerance value.

In other embodiments, the processor may provide a correction value asoutput from the comparison between the estimated orientation and knownorientation of the test pattern 86. In such embodiments, if theestimated orientation and known (i.e., true) orientation do not match(within a tolerance value), a correction value is determined by theprocessor. For example, if the test pattern 86 is at a known angle of30° (as shown in FIG. 8 ), and the estimated angle is determined to be35°, the correction value is calculated as 5°. The correction value isapplied to the orientation of the image sensor 90 by adjusting theorientation of the image sensor 90 via rotation of the image sensor (viathe sub-assembly that attaches the image sensor 90 to the slidingarrangement 66) about a principle axis of the image sensor 90, which maybe the optical axis of the lens 92. The correction value can becalculated as the difference between the estimated angle and the trueangle. In such embodiments, the sign of the correction value can be usedto indicate the required direction of rotation. In certain embodiments,the image sensor 90 is rotated about a principle axis of the imagesensor 90 toward the reference axis (e.g., the axis of horizontalmovement of the image sensor 90) if the correction value is positive,and rotated away from the reference axis if the correction value isnegative. Continuing with the above example of a correction value of 5°,the image sensor 90 is rotated about a principle axis of the lens 92 by5° toward the reference axis

In principle, once the orientation of the image sensor 90 is correctedand properly aligned with the alignment module 80, the image sensor 90can be moved in front of the LOE 70 in order to allow capturing of theimage light waves being coupled out of the LOE 70 in accordance with themethod steps of the focusing and alignment stage. The movement of theimage sensor 90 in front of the LOE 70 is effectuated by moving thesliding arrangement 66 to a second position so as to position the imagesensor 90 in a second location in which the lens 92 of the image sensoris aligned with the LOE 70. Generally speaking, the image sensor 90 ispositioned within the eye motion box, at the eye relief distance fromthe LOE 70, when in the second location. FIG. 7B shows the slidingarrangement 66 in the second position by which the image sensor 90 ispositioned at the second location.

In certain embodiments, the images of the test pattern 86 captured bythe image sensor 90 are grayscale images, for example, 8-bit grayscaleimages. In such embodiments, each image pixel takes on a value between aminimum pixel value and a maximum pixel value. In certainimplementations of 8-bit grayscale images, the minimum pixel value is 0and the maximum pixel value is 255, while in other implementations theminimum pixel value may be −127 and the maximum pixel value may be 128.The pixel values are representative of the amount of light captured ineach specific pixel, with darker pixels corresponding to lower valuesand brighter pixels corresponding to higher values.

As mentioned above, a computerized processor analyzes the images of thetest pattern 86 captured by the image sensor 90. The image analysisperformed by the processor includes the execution of one or more imageprocessing algorithms in order to estimate the angle of the test pattern86. The following paragraphs describe an exemplary image processingalgorithm according to an embodiment of the present disclosure, whichcan be used to estimate the angle of the test pattern 86.

FIG. 9 shows an example of a captured image 88 of the test pattern 86when implemented as a slit. Noise and other interfering factors may addvariations to the edge and end portions of the test pattern 86,resulting in the captured image 88 portraying the test pattern 86 asbeing oblong in shape with various imperfections. For clarity ofillustration, superimposed on the image 88 are a series of horizontalstrips 104 which slice the image 88 into multiple samples. The spacingbetween the strips 104 is preferably uniform, and is a function of thesampling rate of the image 88 executed by the exemplary image processingalgorithm.

For each of the strips 104, jumps from darker edge pixels to bright edgepixels are identified in order to identify points along the edges of theimage 88. In FIG. 9 , the points along the left edge (i.e., side) of theimage 88 are generally indicated as 106, and the points along the rightedge (i.e., side) of the image 88 are generally indicated as 108. Forclarity of illustration, only some of the points on the edges of theimage 88 are labeled.

The jumps may be identified using various mathematical methods. Forexample, the first derivative of the light intensity function of theimage can be evaluated to determine an image gradient. The imagegradient can then be analyzed, specifically by looking for high valuesin the image gradient which correspond to jumps. Edge detectionalgorithms may also be applied in order to identify the jumps, withvarying degrees of accuracy.

Line fitting techniques are used to construct two separate lines, oneline that fits the points 106, and a second line that fits the points108. Examples of such techniques, include, but are not limited to,regression techniques, for example, simple linear regression and totalleast squares, which includes orthogonal regression and Demingregression.

FIG. 10 shows the results of the line fitting, in which a first line 107fits the points 106, and a second line 109 fits the points 108. Theangles of the first line 107 and the second line 109, measured relativeto the reference axis (e.g., axis of horizontal movement of the imagesensor are calculated. The angle of the first line 107 is denoted by a,and the angle of the second line 109 is denoted by β. The angles α and βare averaged together to produce the estimated angle of the test pattern86.

Although the exemplary interpolation-based image processing algorithmhas been described above within the context of the test pattern 86implemented as a rectangular slit, the same or similarinterpolation-based image processing algorithm may be used inembodiments in which the test pattern 86 is implemented as anon-rectangular slit. Regardless of the shape of the test pattern 86,the same basic principles of line fitting edges of the test pattern 86may apply. The angles of the fit lines relative to the reference axiscan be calculated, and the calculated angles for each of the fit linesof the test pattern 86 can be combined, according to mathematicalprinciples (e.g., statistical principles, geometric principles, etc.).

Attention is now directed to FIG. 11 which shows a flow diagramdetailing a process 1100 in accordance with the disclosed subjectmatter. The process 1100 includes steps for aligning the image sensor90. Some of the sub-processes of the process 1100 may be performedmanually by an operator of the environment 1 or may be performedautomatically by various mechanical and computerized components, such asprocessors and the like.

The process 1100 begins at block 1102, where the image projectingoptical device 10 and the LOE 70 are mechanically attached to themechanical assembly, at known and fixed orientations, via the respectivesub-assemblies 61, 63. The process 1100 then moves to block 1104, wherethe image sensor 90 is moved to the first location, i.e., into alignmentwith the alignment module 80. As discussed above, the movement of theimage sensor 90 is facilitated by movement of the sliding arrangement66.

The process 1100 then moves to block 1106, where the image sensor 90captures one or more images of the test pattern. The image of the testpattern 86 may be displayed on the display monitor 100 for viewing bythe operator of the environment 1. The process then moves to block 1108,where each captured image of the test pattern 86 is analyzed, by aprocessor (e.g., an image processor), in order to determine an estimatedorientation (i.e., angle) of the test pattern 86. The estimated anglemay be displayed on the display monitor 100 for viewing by the operatorof the environment 1. In embodiments in which multiple images of thetest pattern 86 are captured, the processor may process each of theimages separately in order to produce multiple estimates of theorientation of the test pattern 86. The multiple estimates may then becombined into a single estimate via averaging or other statisticalmethods known in the art. Alternatively, the processor may co-processthe images together to form a single orientation estimate.

As discussed above, various image processing techniques may be used toestimate the orientation of the test pattern 86. The image processingtechniques include, but are not limited to, line fitting algorithms,edge detection algorithms, and any combination thereof.

From block 1108, the process 1100 moves to block 1110, where the knownorientation of the test pattern 86 and the estimated orientation of thetest pattern 86 (based on the captured image) are compared to form acomparison measure. The comparison measure may be formed, for example,by taking the absolute value of the difference between the estimatedorientation and the known orientation. The process 1100 then moves toblock 1112, where a determination is made, based on the comparisonmeasure output from block 1110, as to whether the estimated orientationis within an allowed tolerance. The determination in block 1112 may bemade, for example, by evaluating the comparison measure against athreshold criterion. For example, the absolute value of the differencebetween the estimated orientation and the known orientation may beevaluated against an allowed tolerance value, to determine if thedifference is greater than the allowed tolerance value or less than (orequal to) the allowed tolerance value. In principle, the allowedtolerance value may be on the order of several hundredths of a degreeand up to one or two tenths of a degree. If the estimated orientation iswithin the allowed tolerance, the process 1100 moves to block 1116 fromblock 1112, where the image sensor 90, now deemed as properly aligned,is moved to the second location, i.e., into alignment with the LOE 70.As discussed above, the movement to the second location is facilitatedby movement of the sliding arrangement 66. The process 1100 then movesto block 1118, where the image sensor 90 captures the image light wavesthat are coupled out of the LOE 70. The execution of block 1118 may beperformed as one or more of the steps performed in the process 500.

If, however, the estimated orientation is not within the allowedtolerance (e.g., not within of the known orientation), the process 1100moves to block 1114 from block 1112, where an orientation parameter ofthe image sensor 90, i.e., the angle about a principle axis of the imagesensor 90 (e.g., the optical axis of the lens 92), is adjusted (i.e.,the image sensor 90 is rotated about its principle axis). From block1114, the process 1100 then returns to block 1106, where a new image ofthe test pattern 86 is captured by the image sensor 90. The blocks1106-1114 are repeated as necessary until the estimated orientation iswithin the allowed tolerance, where the process 1100 moves to block 1116from block 1112, as described above.

The iterative nature of the process 1100 allows an operator of theenvironment 1 to align the image sensor 90 in a relatively short periodof time. In certain embodiments, the image capture, analysis,comparison, determination, and adjustment executed in blocks 1106-1114are performed such that the processor is able to provide the operatorwith a continuous or near-continuous indication of whether the estimatedorientation is within the allowed tolerance. The indication of whetherthe estimated orientation is within the allowed tolerance may bedisplayed visually to the operator of the environment 1, for example viathe display monitor 100.

Note that the allowed tolerance may be a pre-determined value that isprogrammed into a memory of a computer or computing device (e.g., theprocessor or other processing device linked to the processor) that isoperated by operator of the environment 1. In certain embodiments,various tests and experiments may be performed prior to executing themethod steps of the process 1100. Such test and experiments may use theimage sensor 90, the image projecting optical device 10, and the LOE 70,in order to evaluate system performance according to performance metrics(e.g., quality and accuracy of the image coupled out of the LOE 70) as afunction of the orientation error between the image sensor 90 and theLOE 70. The allowed tolerance value may then be determined andprogrammed based on the performance metrics that meet system performancerequirements according to system level specifications. For example, theperformance metrics may indicate that the overall system meetsperformance requirements when the tolerance value is 0.10°, but fails tomeet such requirements when the tolerance value is 0.15°.

Although the embodiments of the process 1100 described above havepertained to image capture, analysis, comparison, determination, andadjustment, as executed in blocks 1106-1114, being performed to allow aprocessor to provide a continuous or near-continuous indication ofwhether the estimated orientation is within the allowed tolerance, otherembodiments are possible in which the processor provides discretecorrection values in response to the comparison performed in block 1110.For example, the comparison output may be treated as a correction value,to be applied to the orientation parameter of the image sensor 90. Insuch embodiments, the orientation parameter of the image sensor 90 isadjusted based on the determined correction value. In such embodiments,the steps of image capture, comparison, and adjustment, as executed inblocks 1106, 1108, and 1114, respectively, may be repeated until theestimated orientation is within a predefined allowed tolerance value(e.g., +/−τ° where τ may be approximately 0.10°).

It is further noted that blocks 1104-1114 may be executed subsequent tothe execution of one or more of the steps described in the process 500,in order to check/correct the alignment of the image sensor 90.Furthermore, subsequent executing blocks 1116-1118, the image projectingoptical device 10 and the LOE 70 may be swapped out for a new imageprojecting optical device and LOE, and the alignment procedure may becontinued to ensure proper alignment of the new image projecting opticaldevice and LOE.

Alternatively, two sets of image projecting optical devices and LOEs,such as used in stereo vision systems, may be deployed and mechanicallyattached to the mechanical assembly (i.e., block 1102 may be performedtwice, once for each LOE/image projecting optical device pair).Subsequent to performing blocks 1104-1114, blocks 1116-1118 may beperformed twice, once for each LOE/image projecting optical device pair.

Although the embodiments of the present disclosure as described thus farhave pertained to utilizing a single image sensor, moveable between twopositions, to alternately capture images of the alignment module 80 andfrom the LOE output, other embodiments are possible in which more thanone image sensor is deployed to capture images. In such embodiments, forexample, two image sensors may be used, with the first image sensoroperating at a lower resolution than the second image sensor. Suchembodiments may be used to advantage in situations in which the focusingand alignment stage is carried out as a coarse-fine process, in whichcoarse adjustments are made based on images captured by the lowerresolution image sensor, and fine adjustments are made based on imagescaptured by higher resolution image sensor.

In discussing the execution of the steps of the processes 500 and 1100,references were made to the movement of various mechanical and opticalcomponents, as well as the execution of image processing functions. Thefollowing paragraphs describe non-limiting examples of instrumentation(i.e., components) and techniques used to perform the method stepsassociated with the processes 500 and 1100.

Instrumentation and Techniques for Performing Focusing and AlignmentStage and Orientation Alignment Stage

As discussed in detail above, several of the method steps associatedwith the processes 500 and 1100, in particular blocks 506 and 508 of theprocess 500, and block 1108 of the process 1100, are performed by theexecution of various image processing techniques. The image processingtechniques may be executed by a computerized processor, which may bepart of a processing system. In addition, several of the method stepsassociated with the process 1100, in particular blocks 1110 and 1112,involve performing logic operations including comparisons anddetermining whether outputs from the comparisons satisfy thresholdcriteria (i.e., whether the absolute difference between the estimatedorientation and the known orientation is greater than or less than anallowed tolerance value). Such logic operations, in the form ofcomparisons and evaluations against threshold criteria, are preferablyperformed by computerized processors, which in certain embodiments isthe same processor that performs the image processing techniques.

FIG. 12 shows a block diagram of an example architecture of such aprocessing system, generally designated 110 that includes at least onecomputerized processor. The processing system 110 is linked to the imagesensor 90 and the display monitor 100, such that processing system 110can receive image data from the image sensor 90, and provide processedoutput to the display monitor 100 for display.

The processing system 110 includes at least one processor 112 coupled toa storage module 114 such as a memory or the like. The processor 112 canbe implemented as any number of computerized processors, including, butnot limited to, a microprocessor, an ASIC, and a DSP. In certainnon-limiting implementations, the processor 112 is advantageouslyimplemented as an image processor. All of such processors include, ormay be in communication with non-transitory computer readable media,such as, for example, the storage module 114. Such non-transitorycomputer readable media store program code or instructions sets that,when executed by the processor 112, cause the processor 112 to performactions. Types of non-transitory computer readable media include, butare not limited to, electronic, optical, magnetic, or other storage ortransmission devices capable of providing a processor, such as theprocessor 112, with computer readable instructions.

In certain embodiments, the processor 112 is configured to perform imageprocessing functions, in accordance with blocks 506 and 508 of theprocess 500, and block 1108 of the process 1100, and is furtherconfigured to perform other various logic functions, for example inaccordance with blocks 1110 and 1112 of the process 1100. In embodimentsin which determinations are made as to whether the estimated orientationis within an allowed tolerance, the storage module 114 may be configuredto store the allowed tolerance value (or values). Alternatively, theallowed tolerance value may be stored in a volatile or non-volatilememory of the processor 112. In other embodiments, the variousaforementioned image processing and logic functions are performed byseparate processors, which are part of the same processing system 110,or may be part of separate similar processing systems that are linked toeach other.

In embodiments in which differences between the estimated orientationand known orientation are used to determine a correction value to beapplied to the orientation parameter of the image sensor 90, theprocessor 112 may be configured to determine the correction value.

As further discussed above, the image processing steps are executed inconjunction with movement of various mechanical and optical components.Such movement is outlined in the method steps associated with theprocesses 500 and 1100, in particular blocks 506-508 of the process 500,and blocks 1104, 1114 and 1116 of the process 1100. As discussed, themovement of the aforementioned components is enabled by varioussub-assemblies of the mechanical assembly 60. The following paragraphs,with reference to FIGS. 13 and 14 , describe a more detailednon-limiting schematic representation of the mechanical assembly 60according to an embodiment of the present disclosure, that can be usedwhen performing the steps of the processes 500 and 1100.

As shown in FIG. 13 , the mechanical assembly 60 includes a base 602that is generally planar and extends between to ends, namely a first end604 and a second end 606. A sliding rail 608 is mechanically attached,via screws or the like, to the base 604 and extends between the two ends604, 606. A stand 610 extends upward from the base near the second end606. The stand 610 is fixedly mounted to the base 602 via mechanicalfasteners, such as screws or bolts and the like. The sliding rail 608and a base 612 of the sliding arrangement 66 are correspondinglyconfigured, so as to allow the sliding arrangement 66 to move laterallyacross the base 602 between the two ends 604, 606. The slidingarrangement 66 has a stand 614 that extends upward from the base 612,and that is mechanically attached to the base 612 via mechanicalfasteners, such as screws or bolts and the like. The image sensor 90 ismechanically coupled to a top portion 615 (i.e., distal portion from thebase 612) of the stand 614 via a mechanical sub-assembly that allowsadjustment of the orientation of the image sensor 90.

In certain embodiments, stoppers may be deployed at different positionsalong the sliding rail 608, for example at or near the horizontalposition of the LOE 70 and the alignment module (i.e., the test pattern86). In this way, the sliding arrangement 66 may move between tworesting positions, so as to alternately align with the LOE 70 and thealignment module 80. In certain embodiments, the movement of the slidingarrangement 66 is manually induced (i.e., hand-operated by a user of theoptical test bench). In other embodiments, the sliding arrangement 66 iselectro-mechanically operated, and movement thereof is enabled by adriving arrangement (e.g., actuator with mechanical linkage) coupled toa computer or computing device that allows the user of the optical testbench (i.e., the environment 1) to actuate movement of the slidingarrangement 66 between the resting positions via a user interface or thelike implemented on the computer or computing device. In still yet otherembodiments, the movement of the sliding arrangement 66 is manuallyinduced and aided by an electro-mechanical driving arrangement.

FIG. 13 also shows a member 616 deployed relative to the stand 610. Themember 616 is a schematic representation of the LOE 70, the collimatingprism assembly 18, and the second sub-assembly 63 which fixedly mountsthe LOE 70 and the collimating prism assembly 18 to the stand 610 of themechanical assembly 60 in a fixed and known orientation. Although thecollimating prism assembly 18 may be considered as one of the componentsof the image projecting optical device 10, the collimating prismassembly 18 may be attached to the LOE 70 via an optical attachment(e.g. cement) or a mechanical attachment (e.g., a bracket arrangement orthe like). The mounting of the member 616 to the mechanical assembly 60is made via mechanical attachment of the second sub-assembly 63 to anupper portion of the stand 610. The second sub-assembly 63 may includeone or more brackets and/or one or more stoppers arranged to hold theLOE 70 in a known and fixed position and orientation relative to themechanical assembly 60.

The single unit 50 is positioned behind the member 616. The single unit50 is a mechanical body that holds the electronic display source 12, theillumination module 14, and the illumination prism assembly 16. FIG. 14shows a more detailed illustration of the single unit 50, as well as thefirst sub-assembly 61, according to a non-limiting example construction.In the non-limiting construction, the first sub-assembly 61 isimplemented as a double clamping arrangement, that includes an upperclamping member 618 and a lower clamping member 620, configured to holdthe single unit 50. The clamping members 618, 620 respectively hold thetop and bottom portions of the single unit 50, and are connectedtogether by a central pin 622 and an end joint 624. The single unit 50may be formed as a closed or semi-closed box-like structure having theelectronic display source 12, the illumination module 14, and theillumination prism assembly 16 housed therein. In the non-limitingconstruction shown in FIG. 14 , the electronic display source 12 iscoupled to the housing via a base plate and mechanical fasteners (e.g.,screws).

Although not shown in the drawings, the joint 624 is mechanicallyattached to the stand 610 via a mechanical linkage. An arrangement ofadjustment mechanisms (e.g., knobs, dials, etc.) are coupled to themechanical linkage to facilitate the adjustable positioning of the firstsub-assembly 61 relative to the member 616, so as to allow for thedisplacing and translational moving of the single unit 50 in accordancewith the process 500.

With respect to the displacement described in block 506, and thetranslational movement described in block 508, the displacing andtranslational actions may be performed by applying force to one or moresub-components of the first sub-assembly 61. In certain embodiments, thedisplacing and translational actions are induced manually (i.e.,hand-operated) by an operator/user operating one or more of theadjustment mechanisms coupled to the mechanical linkage. Such manualoperations may include, for example, hand operation of the one or moreadjustment mechanisms, which may include, for example, turning of knobsor dials. For example, turning one set of knobs or dials may displacethe single unit 50 by an incremental amount in proportion to the amountand direction of turn of the knob/dial. Similarly, turning another setof knobs or dials may translate the single unit 50 an incremental amountin proportion to the amount and direction of turn of the knob/dial.

It is noted that in principle the displacement and translational amountsare typically on the order of several micrometers (e.g., tens ofmicrometers and possibly up to a few hundred micrometers), and manytypes of equipment used in optical laboratory test benches providemechanical assemblies and instruments capable of accommodating smalladjustment amounts based on hand-operation of the such instruments.

In practice, one or more slabs of glass may be placed between the singleunit 50 and the member 616 to provide an interface region between theillumination prism assembly 16 and the collimating prism assembly 18. Asan example, the slabs may be positioned between the adjacentlight-transmissive surfaces 36 and 38 of the prism assemblies 16, 18.After the single unit 50 is displaced and translationally moved (per themethod steps of the process 500), optical cement may be applied betweenthe slabs and the adjacent surfaces of the prism assemblies 16, 18 toform an optical attachment between the prism assemblies 16, 18.

Returning to FIG. 13 , the alignment module 80 is mechanically coupledto a side portion of the stand 610 via the third sub-assembly 65. Thethird sub-assembly 65 is attached to the side portion of the stand 610near the member 616. In the schematic representation of the mechanicalassembly 60 illustrated in FIG. 13 , the third sub-assembly 65 includesan extending arm 628 that is mechanically attached, at a first end 626,to the side portion of the stand 610. The mechanical attachment of theextending arm 628 to the stand 610 is made via mechanical fasteners,such as screws or the like. A base plate 630 is deployed at a second endof the extending arm 628. The test pattern 86 is arranged on the baseplate 630. Although not shown in FIG. 13 , the light source 82 and thediffuser 84 are attached to the back side of the base plate 630 (i.e.,behind the test pattern 628).

It is noted that the attachment of the LOE 70 and the alignment module80 to the mechanical assembly 60 is performed prior to the execution ofthe steps of the alignment methodologies described in the presentdisclosure. The LOE 70 is attached to the mechanical assembly 60 in afixed orientation, such that, when the image sensor 90 is positioned inthe eye motion box at the eye relief distance, image capture (by theimage sensor 90) of the entire image (i.e., full FOV) projected by theLOE 70 is enabled. The attachment of the LOE 70 and the alignment module80 to the mechanical assembly 60 is made using various types of opticaltest equipment known in the art, including, for example,autocollimators, which facilitate attachment of the aforesaid componentsto the mechanical assembly 60 in known and fixed orientations withrelatively high accuracy levels. In this way, a linkage is establishedbetween the orientation of the alignment module 80 and the orientationof the LOE 70, such that correction of the alignment of the image sensor90 relative to the alignment module 80 ensures proper alignment of theimage sensor 90 relative to the LOE 70 as well.

Although the displacing and translational actions of the single unit 50,as described above, may be induced via hand-operation of one or moreadjustment mechanisms of the mechanical assembly 60, other embodimentsare possible, in which such adjustment mechanisms are operated by anelectro-mechanical control system.

FIG. 15 is a block diagram of an example architecture of such anelectro-mechanical control system, generally designated 120. Theelectro-mechanical control system 120 is linked to the processing system110 and includes a controller 122 and an actuator 124. The controller122 can be implemented as any number of computerized processors,including, but not limited to, a microcontroller, a microprocessor, anASIC, and a DSP. All of such processors include, or may be incommunication with non-transitory computer readable media that storesprogram code or instructions sets that, when executed by the controller122, cause the controller 122 to perform actions. Types ofnon-transitory computer readable media include, but are not limited to,electronic, optical, magnetic, or other storage or transmission devicescapable of providing a processor, such as the controller 122, withcomputer readable instructions.

The actuator 124 may be a mechanical actuator, for example a steppermotor, that causes the displacing and translational actions by applyingforce to one or more sub-components of the first sub-assembly 61 inresponse to controlled input from the controller 122. The controller 122may receive image quality metrics, such as the focus quality and LoSevaluation, as input from the processing system 110, so as to providefeedback control to the actuator 124 to adjust the adjustment mechanismsbased on the focus quality and LoS evaluation.

In certain embodiments, the actuator 124 may also control the adjustmentof the orientation parameter of the image sensor 90. In suchembodiments, the actuator 124 causes rotational adjustment by applyingforce to the sub-assembly that attaches the image sensor 90 to thesliding arrangement 66. The actuator 124 induces such rotationaladjustment in response to controlled input received from the controller122. The controlled input is provided by the controller 122 in responseto output from the processing system 110 indicative of whether theestimated orientation is within the allowed tolerance, in accordancewith block 1112. The processing system 110 and the electro-mechanicalcontrol system 120 may together form a closed loop system that enablesconvergence to within the allowed tolerance value. In such a closed loopsystem, the electro-mechanical control system 120 actuates the imagesensor 90 to capture images of the test pattern 86. Theelectro-mechanical control system 120 then adjusts the orientationparameter of the image sensor 90 in response to input from theprocessing system 110 derived from image analysis performed on thecaptured images of the test pattern 86. The actuation, adjustment, andimage analysis functions, performed by the electro-mechanical controlsystem 120 and the processing system 110, are repeated until theestimated orientation (from the image analysis) is within the allowedtolerance value.

In certain embodiments, the actuator 124 may also control the movementof the sliding arrangement 66. In such embodiments, the actuator 124receives controlled input from the controller 122 to slide the slidingarrangement 66 between the first and second positions. In suchembodiments, the controller 122 is preferably linked to a computer orcomputing device having a user interface implemented thereon, to allowthe operator to provide input commands to the controller 122 in order toinitiate controlled movement of the sliding arrangement 66.Alternatively, the motion of the sliding arrangement 66 may be fullyautomated by the controller 122.

Note that in certain embodiments, the image processing and controlfunctionality may be implemented by a single processing-controlsubsystem having one or more processors.

Description of Example Waveguide Implementations

As discussed above, when performing the method steps of the alignmentmethods of embodiments of the present disclosure, the image sensor 90captures image light waves that are coupled out of the LOE 70. The LOE70 functions as an optical waveguide that guides light waves from aninput optical surface to an output optical surface. In certainnon-limiting implementations, the image light waves from the imageprojecting optical device 10 are coupled into the LOE 70 and are guidedthrough the LOE 70, by total internal reflection. The guided light wavesare then coupled out of the LOE 70 as image light waves by one or morepartially reflecting surfaces. When in use by the end-user (i.e.,subsequent to final assembly in eyeglasses or the like), the coupled-outlight waves are projected into an eye (or eyes) of the user (i.e.,viewer).

FIG. 16 illustrates an example of an implementation of an LOE. The LOEis formed of a light waves-transmitting planar substrate 130 thatincludes a major lower surface 132 and a major upper surface 134 thatare parallel to each other. A coupling-in optical element 136 isilluminated by collimated light waves (represented by optical ray 138)from the image projecting optical device 10. The coupling-in opticalelement 136 includes a slanted edge 140 of the substrate 130 and a prism142. The edge 140 is oriented at an oblique angle with respect to themajor lower and upper surfaces 132, 134 of the substrate 130, whereinα_(edge) is the angle between the edge 140 and the normal to the majorlower and upper surfaces 132, 134 of the substrate 130. The prism 142includes three major surfaces 144, 146, 148, with the surface 144 beinglocated next to the edge 140 of the substrate 130, and surfaces 146 and148 being polished surfaces. In certain embodiments, the refractiveindex of the prism 142 is similar to the refractive index of thesubstrate 130, while in other embodiments the prism 142 and thesubstrate 130 have different refractive indices. The optical ray 138enters the prism 142 through the surface 146. The surface 146 ispreferably oriented normally to the central light wave of the incomingray (i.e., the optical ray 138). The optical ray 138 then passes throughthe surface 144 to enter the substrate 130 through the edge 140, wherebythe optical ray 138 is trapped inside the planar substrate 130 of theLOE by total internal reflection. After several reflections of the majorlower and upper surfaces 132, 134 of the substrate 130, the trappedwaves reach a coupling-out optical arrangement 150, implemented forexample, as an array of selective partially reflecting surfaces, whichcouple the light waves out of the substrate 130 out of the substrate130.

When the LOE of FIG. 16 is used as the LOE 70 when performing the methodsteps of the alignment methods of embodiments of the present disclosure,the coupling-out optical arrangement 150 couples the light waves out ofthe substrate 130 so that the coupled-out light waves may be captured bythe image sensor 90.

Note that although FIG. 16 depicts the input surface of the LOE (i.e.,the surface through which the input light waves enter the LOE) is on theslanted edge 140 and the output surface of the LOE (i.e., the surfacethrough which the trapped waves exit the LOE) is on the lower majorsurface 132, other configurations are envisioned. In one suchconfiguration, the input and output surfaces could be located on thesame side of the substrate 130. In such a configuration, the coupling-inoptical element 136 may be realized by a reflecting surface that isoriented at an oblique angle with respect to the major lower and uppersurfaces 132, 134 of the substrate 130, such that the input surface ofthe LOE is on the major lower surface 132 and the coupling-in reflectingsurface reflects the incident light waves such that the light is trappedinside the substrate 130 by total internal reflection. Still yet otherconfigurations are envisioned in which the input surface is on the majorupper surface 134 and the output surface is on the major lower surface132.

When the LOE of FIG. 16 is in use by the end-user, the coupled-out lightwaves are projected into an eye (or eyes) of the user (i.e., viewer).Specifically, the coupling-out optical arrangement 150 couples the lightwaves out of the substrate 130 into a pupil 154 of an eye 152 of theviewer, which form an image viewed by the viewer. The eye 152 ispositioned at the eye relief distance 156 from the LOE 70, and withinthe eye motion box 158. As discussed above, the eye motion box 158 is atwo-dimensional area at the eye relief distance 156 at which the eye 152captures the entire image (i.e., full FOV) projected by the LOE 70.

In certain embodiments, the LOE 70, together with the image projectingoptical device 10, provides an augmented reality environment for theuser in which the images from the image projecting optical device 10that are coupled out of the LOE 70 can be overlaid on the real-worldscene. In such embodiments, images from the real-world scene passdirectly through the major lower and upper surfaces 132, 134 of thesubstrate 130 into the eye of the viewer, while the LOE simultaneouslycouples images (i.e., virtual images) from the image projecting opticaldevice into the eye 152. In other embodiments, the LOE 70, together withthe image projecting optical device 10, provides a virtual realityenvironment for the user in which only the virtual images from the imageprojecting optical device 10 are viewed by the user. In suchembodiments, external real-world scene images are not transmitted thoughthe substrate 130.

The LOE can be used as part of a mono-ocular optical system, in whichimages are projected into a single eye of the viewer. Alternatively, itmay be desirable to project images into both eyes of the viewer, such asin head-up display (HUD) applications and stereo vision systems. In suchalternatives, two optical systems can be used, with each optical systemhaving an image projecting optical device and an LOE deployed forprojecting images into a different eye of the viewer. For example, a HUDemploying two optical systems may be installed in front of a car driver,for example integrated into the dashboard of a vehicle, so as to provideassistance in driving navigation or to project thermal images into theeyes of the driver in low-visibility conditions. In such embodiments, athermal camera may be deployed to capture thermal images of thereal-world scene. The thermal images may then be provided to the imageprojecting optical device 10 to enable coupling-in of light wavescorresponding to the thermal images into the LOE.

The alignment methods of the embodiments of the present disclosure canbe used to advantage in dual-optical systems (i.e., two LOE/imageprojecting optical device pairs), such as in HUD applications and stereovision systems, which require proper alignment of the components of eachLOE/image projecting optical device pair, as well as alignment of thetwo optical systems with each other, to ensure correct stereo images.

Although the alignment methods of the embodiments of the presentdisclosure have been described within the context of an opticalwaveguide implemented as an LOE, for example the LOE 70 of FIG. 16 , thealignment methods of the present disclosure may be applicable to othertypes of optical waveguide technologies, including waveguides that relyon diffractive techniques to couple light waves into and/or out of alight waves-transmitting substrate. For example, instead of implementingthe coupling-out optical arrangement 150 as an array of selectivelypartially reflecting surfaces, the coupling-out optical arrangement 150can be implemented as one or more diffractive elements that extendsalong portions of the major lower surface 132 of the substrate 130. As afurther example, instead of the implementing the coupling-in opticalelement 136 as a slanted edge 140 together with a prism 142, or as areflecting surface oriented at an oblique angle, the coupling-in opticalelement can be implemented as a diffractive element that extends along aportion of the either the major lower surface 132 or the major uppersurface 134.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

As used herein, the singular form, “a”, “an” and “the” include pluralreferences unless the context clearly dictates otherwise.

The word “exemplary” is used herein to mean “serving as an example,instance or illustration”. Any embodiment described as “exemplary” isnot necessarily to be construed as preferred or advantageous over otherembodiments and/or to exclude the incorporation of features from otherembodiments.

It is appreciated that certain features of the invention, which are, forclarity, described in the context of separate embodiments, may also beprovided in combination in a single embodiment. Conversely, variousfeatures of the invention, which are, for brevity, described in thecontext of a single embodiment, may also be provided separately or inany suitable subcombination or as suitable in any other describedembodiment of the invention. Certain features described in the contextof various embodiments are not to be considered essential features ofthose embodiments, unless the embodiment is inoperative without thoseelements.

Although the invention has been described in conjunction with specificembodiments thereof, it is evident that many alternatives, modificationsand variations will be apparent to those skilled in the art.Accordingly, it is intended to embrace all such alternatives,modifications and variations that fall within the spirit and broad scopeof the appended claims.

What is claimed is:
 1. A method for aligning an image sensor with anoptical device, the method comprising: mechanically coupling at leastone component of the optical device to a mechanical assembly at a knownorientation, the mechanical assembly having a test pattern at a knownorientation; capturing an image of the test pattern when the imagesensor is positioned at a first location in which the image sensor isaligned with the test pattern; analyzing the captured image to determinean estimated orientation of the test pattern; and adjusting anorientation parameter of the image sensor based on a comparison betweenthe known orientation of the test pattern and the estimated orientationof the test pattern.
 2. The method of claim 1, further comprising:capturing an image projected by the optical device when the image sensoris positioned at a second location in which the image sensor is alignedwith the optical device.
 3. The method of claim 1, wherein the opticaldevice includes an image projecting device and a lightwaves-transmitting substrate, the method further comprising: couplinglight waves, corresponding to an image projected by the image projectingdevice, into the light waves-transmitting substrate; coupling thecoupled-in light waves out of the substrate as image light waves; andcapturing the image light waves with the image sensor when the imagesensor is positioned at a second location in which the image sensor isaligned with the light waves-transmitting substrate.
 4. The method ofclaim 1, wherein the orientation parameter of the image sensor includesan angle of rotation about a principle axis of the image sensor.
 5. Themethod of claim 1, wherein the test pattern is vertically orientedrelative to a reference axis.
 6. The method of claim 1, wherein the testpattern is horizontally oriented relative to a reference axis.
 7. Themethod of claim 1, wherein the test pattern is oriented at an obliqueangle relative to a reference axis.
 8. The method of claim 1, whereinthe orientation of the test pattern is defined by at least oneorientation parameter, and wherein the at least one orientationparameter of the test pattern includes an angular position of the testpattern relative to a reference axis.
 9. The method of claim 1, whereinthe test pattern is formed as an aperture in the mechanical assembly.10. The method of claim 1, further comprising: illuminating the testpattern.
 11. The method of claim 1, further comprising: moving the imagesensor to the first location prior to capturing the image of the testpattern; and moving the image sensor to the second location aftercapturing the image of the test pattern.
 12. The method of claim 1,wherein the optical device includes at least a display source, anillumination module, an illumination prism assembly, and a collimatingprism assembly.
 13. The method of claim 12, further comprising: aligningthe illumination module and the display source with the illuminationprism assembly such that light waves emitted by the illumination modulearrive at the display source via the illumination prism assembly;displacing the display source along a displacement axis to adjust adistance between the display source and the collimating prism assembly;and translationally moving, in unison, the display source, theillumination prism assembly, and the illumination module in a planenormal to the displacement axis.